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> the mean difference Yes, but later the article shows that "mean difference" is really mean difference divided by variance. > an important point is that whet

by pron 7y ago

> the mean difference Yes, but later the article shows that "mean difference" is really mean difference divided by variance. > an important point is that whether something qualifies is really a question of the scale It's one of the concerns, but I would say it's the main one. An effect size needs to distinguish between the two cases here, both having the same expected difference: https://imgur.com/a/hg2NNl2 https://imgur.com/a/hg2NNl2 If you care about units, you can talk about the expected value/difference, but that doesn't make that a meaningful effect size. What you need to do in those cases is to, at least, mention both the expected difference and the variance.

closed 7y ago
> Yes, but later the article shows that "mean difference" is really mean difference divided by variance. I would say later the article shows examples of standardized effect size, so divides by variance. Whether that means effect size can't be a difference in means (and explains the wiki intro comment) I disagree with--see my Lakens comment for why. > If you care about units, you can talk about the expected value/difference, but that doesn't make that a meaningful effect size. What you need to do in those cases is to, at least, mention both the expected difference and the variance. This seems like it is begging the question. If you look at the definition and rationale for effect size, both in the wikipedia and in Lakens, a claim this strong is not there. For example, a CI over difference in means is one way to capture what a standardized effect size that uses a specific variance term might be doing (what Lakens describes as the second ES viewpoint: statistical significance, distinguishing between effect and power). In any event, thanks for discussing--it's been really helpful to think about and revisit this topic!

by pron 7y ago

closed 7y ago

> Yes, but later the article shows that "mean difference" is really mean difference divided by variance. I would say later the article shows examples of standardized effect size, so divides by variance. Whether that means effect size can't be a difference in means (and explains the wiki intro comment) I disagree with--see my Lakens comment for why. > If you care about units, you can talk about the expected value/difference, but that doesn't make that a meaningful effect size. What you need to do in those cases is to, at least, mention both the expected difference and the variance. This seems like it is begging the question. If you look at the definition and rationale for effect size, both in the wikipedia and in Lakens, a claim this strong is not there. For example, a CI over difference in means is one way to capture what a standardized effect size that uses a specific variance term might be doing (what Lakens describes as the second ES viewpoint: statistical significance, distinguishing between effect and power). In any event, thanks for discussing--it's been really helpful to think about and revisit this topic!